The basic parts of most footwear articles, regardless of their specific type, are a sole and a top part. The sole protects the wearer's foot from direct contact with the ground, while the top part keeps the foot secured to the shoe when the foot is lifted off the ground. In what is often referred to as “closed shoes,” the top part covers a substantial portion of the foot, and is normally connected to the sole by a strip of material called a “welt.” Sometimes, the welt and the top part are combined. In so-called “open shoes,” such as flip-flops or sandals, there is often only minimal structure holding onto the foot or parts thereof from the top. Strings and straps of various types are common examples.
An extreme case of “open shoes” is what is commonly known as “stick on sandals,” “stick on flip-flops,” etc., in which a sole is attached to the foot solely by adhesive forces. The top surface of these soles exhibits adhesive properties, sufficient to remain clung to the sole of the foot under relatively relaxed walking conditions. A further variation of such sandals is the type which clings to the foot using various suction elements instead of an adhesive.